Pharmacologically active antiviral peptides and methods of their use

ABSTRACT

This invention relates to peptides having antiviral properties. The antiviral peptides comprise membrane transiting peptides, and active fragments and derivatives of such peptides. The antiviral peptides exhibit activity against a broad spectrum of viruses, including enveloped and nonenveloped viruses, and are used in pharmaceutical compositions to prevent and/or treat viral infections.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 09/777,560, filed Feb. 6, 2001, now U.S. Pat. No. 7,371,809, whichclaims priority to U.S. Provisional Patent Application Nos. 60/184,057,filed Feb. 2, 2000 and 60/180,823, filed Feb. 7, 2000, the entirecontents of which are hereby incorporated by reference.

GOVERNMENT SUPPORT Statement as to Rights to Inventions Made UnderFederally-Sponsored Research and Development

This invention was made with United States Government support awarded bythe following agency: DOD ARPA Grant No. MDA972-97-1-0005. The UnitedStates Government has certain rights in this invention.

FIELD OF THE INVENTION

This invention relates to peptides having antiviral properties. Morespecifically, the invention relates to peptides exhibiting activityagainst a broad spectrum of viruses, to pharmaceutical compositionscomprising the peptides, and to methods of using the peptides to preventand/or treat viral infections.

BACKGROUND OF THE INVENTION

In recent years, various groups of peptide derivatives having activityagainst viruses have been disclosed. Examples of these peptides aredisclosed in U.S. Pat. No. 5,700,780, issued to Beaulieu et al.; U.S.Pat. No. 5,104,854, issued to Schlesinger et al.; U.S. Pat. No.4,814,432 issued to Freidinger et al.; Dutia et al., Nature 321:439(1986); and Cohen et al., Nature 321:441 (1986). However, many of theknown antiviral peptides known in the art are extremely hydrophobic, andtherefore, not very bioavailable. Moreover, many of these knownantiviral peptides show activity against only a few types of viruses,due to their particular mechanisms of action. Additionally, many ofthese synthetic peptides are not effective in preventing initial viralinfection, or are not functional when applied topically.

One of the most successful nucleoside analogs developed as an antiviralagent to-date is acyclovir. Acyclovir is a synthetic purine nucleosideanalog with in vitro and in vivo inhibitory activity against herpessimplex virus type I (HSV-1), herpes simplex virus type II (HSV-2), andvaricella zoster virus (VZV). In cell culture, acyclovir's highestantiviral activity is against HSV-1, followed in decreasing order ofpotency against HSV-2 and VZV. However, the use of acyclovir may becontraindicated. Moreover, some herpes simplex viruses have becomeresistant to acyclovir.

Recently, there has been considerable research into antiviral compoundsthat could be incorporated into topical virucides and condom lubricantsto help stem the spread of human immunodeficiency virus (HIV). The needfor such a product is high; the appropriate antiviral and/or virucidalcompound that prevents HIV infection would be of great use in bothdeveloped and undeveloped nations.

Therefore, there remains a need for antivirals which exhibit a highactivity against a broad spectrum of viruses. There also remains a needfor antivirals that can be applied topically, and are effective atpreventing viral infection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1D, and FIG. 1E are graphical representations showing thedose-dependent inhibition of HSV-1 by an antiviral peptides of thepresent invention (SEQ ID NO:1), (SEQ ID NO:3) and (SEQ ID NO:4)compared to control peptides (SEQ ID NO:16 and SEQ ID NO:17). FIG. 1Cshows the cytotoxic effects of SEQ ID NO:1 and SEQ ID NO:17.

FIG. 2 is a graphical representation showing viral inhibition by abiotinylated antiviral peptide (SEQ ID NO:2) of the present invention.

FIG. 3 is a graphical representation showing the dose-dependentinhibition of HSV-1 formation by an antiviral peptide of the presentinvention (SEQ ID NO:1) as compared to acylovir.

FIGS. 4A and 4B are graphs illustrating that an antiviral peptide of thepresent invention (SEQ ID NO:1) inhibits an early stage of virusinfection and virus spreading.

FIG. 5 is a graph illustrating the antiviral activity of an antiviralpeptide of the present invention (SEQ ID NO:1) is dependent on virusinput.

FIGS. 6A and 6B are graphs illustrating the blocking of viral entry intocells by an antiviral peptide of the present invention (SEQ ID NO:1).

FIGS. 7A and 7B are graphs illustrating the entry phase and doseresponse of an antiviral peptide of the present invention (SEQ ID NO:1).

FIGS. 8A and 8B are graphs illustrating the virucidal activity of anantiviral peptide of the present invention (SEQ ID NO:1).

FIGS. 9A and 9B are graphs illustrating the in vivo activity of anantiviral peptide of the present invention (SEQ ID NO:1).

DETAILED DESCRIPTION OF THE INVENTION

In the description that follows, a number of terms are utilizedextensively. Definitions are herein provided to facilitate understandingthe invention.

Antiviral peptide: The antiviral peptide comprises at least in part amembrane transiting peptide, or a fragment or a derivative thereof, thatis a pharmacologically effective antiviral agent when administered in aneffective amount.

Effective amount: A predetermined amount of the antiviral peptide, i.e.,an amount of the peptide sufficient to be effective against the viralorganisms in vivo or topically for treatment or prophylactic effect.

Membrane transiting peptide (membrane transiting motif): A peptidehaving a sequence of amino acids that render the peptide capable oftraversing lipid bilayer membranes to enter cells or subcellularcompartments.

Pharmaceutically acceptable carrier: An acceptable cosmetic vehicle foradministering antiviral peptides to mammals comprising one or morenon-toxic excipients which do not react with or reduce the effectivenessof the pharmacologically active antiviral peptide contained therein.

Solubility tag: a short peptide sequence comprised of charged aminoacids which, when attached to a terminal residue of a longer insolublepeptide sequence, will improve solubility in an aqueous medium.

In this application, the standard one letter abbreviated names for theamino acids are used throughout. See Lehninger et al. “Principles ofBiochemistry”, Worth Publishers (New York, N.Y.) p. 113 (1983). Allamino acid sequences in this application are depicted using standardnomenclature, with the left most amino acid residue at the end of eachsequence being the amino-terminal residue and the residue at the rightend of each sequence being the carboxyl-terminal residue. The aminoacids of the peptides described herein may be either levo amino acids ordextro amino acids, as denoted 1 or d before the peptide sequence (SeeTable 1).

The present invention relates to novel antiviral peptides which arebased on membrane transiting peptides. Various membrane transitingpeptides are well known in the art. It has been surprisingly andunexpectedly discovered that membrane transiting peptides exhibit abroad spectrum of antiviral activity, including such activity whenapplied topically or administered in vivo. Exemplary antiviral peptidesof the present invention derived from membrane transiting peptides aredescribed below Table 1, although any membrane transiting peptide knownin the art may be used, see, e.g., Pooga et al., FASEB J., 12:67 (1998)and Oehlke et al., FEBS Lett., 415:196 (1997).

TABLE 1 Antiviral Peptides SEQUENCE Peptide ID NUMBER Sequence EBSEQ ID NO:1 NH₂- RRKKAAVALLPAVLLALLAP-COOH bEB SEQ ID NO:2 b - RRKKAAVALLPAVLLALLAP-COOH EBPP SEQ ID NO:3NH₂- RRKKAAVALLAVLLALLAPP-COOH LALA SEQ ID NO:4 NH₂- RRKKPAVLLALLA-COOHbKLA SEQ ID NO:5  b - KLALKLALKALKAALKLA-amide bKLAd_(11,12) SEQ ID NO:6

bHOM-9 SEQ ID NO:7  b - RQIKIWFPNRRMKWKK-9 bHOMd SEQ ID NO:8

bHOMFF SEQ ID NO:9  b - RQIKIFFPNRRMKFKK-amide bTAT-9 SEQ ID NO:10 b - YGRKKRRQRRR-9 bTAT-9x SEQ ID NO:11  b - YGRKKRRQRRR-9xN^(E13)-biotinyl transportan SEQ ID NO:12

VT5 SEQ ID NO:13 fluor-DPKGDPKGVTVTVTVTVTGKGDPKPD Residues indicated inbold are positively charged residues b = biotin-aminohexanoyl d =peptide composed of all D amino acid residues fluor = fluorescent label-9 = PGYAGAVVNDL-COOH -9x = PGDVYANGLVA-COOH

The antiviral peptides of the present invention may be used alone in aneffective amount. Although most membrane transiting peptides aresoluble, some are not, although insoluble membrane transiting motifs maybe utilized in antiviral peptides by the following method. If theantiviral peptide is insoluble in an aqueous pharmaceutically acceptablecarrier, a solubility tag may be added to the antiviral peptide.

As shown in Table 1, SEQ ID NOS: 1-4 have had a solubility tagcovalently attached. The present invention relates to such novelantiviral peptides which in part comprise a solubility tag covalentlyattached and have the following sequence:(X1)_(n)-A-A-V-A-L-L-P-A-V-L-L-A-L-L-A-P-(X2)_(m) (SEQ ID NO:14) or(X1)_(n)-P-A-V-L-L-A-L-L-A-(X2)_(m) (SEQ ID NO:15) wherein X1 and X2 areselected from one or more charged amino acid residues (e.g. K, R) whereeach X1 and each X2 may be the same or different charged amino acidresidue; and wherein n has a value of 0 or 3-10, and m has a value of 0or 3-10, wherein in one embodiment either m=0 or n=0. One example of asolubility tag is R-R-K-K (SEQ ID NO:16). In the preferred embodiment,all charged amino acid residues of the solubility tag are positivelycharged amino acid residues. The inventors have surprising andunexpectedly discovered that insoluble membrane transiting peptides,when coupled to a solubility tag, create antiviral peptides that exhibitstrong antiviral activity against a broad spectrum of viruses.

Many membrane transiting peptides may function as antiviral peptides ofthe present invention without the need for solubility tags. See Table 1.Moreover, although solubility tags may improve the solubility of somemembrane transiting peptides, these particular membrane transitingpeptides may be suitable as antiviral peptides without incorporatingsolubility tags.

The antiviral peptides of the present invention may have variousreactive tags attached to their terminal amino acid residues. Such tagsmay be useful in detection/removal of the synthetic peptides of thepresent invention. Such tags may include, by way of example only,biotin, as well as any other tags well-known in the art. SEQ ID NOS: 2,5-12 and Example 2 demonstrate the inclusion of such reactive tags.

Derivatives and fragments of membrane transiting peptides of the presenthave also been found to be useful as antiviral peptides. The presentinvention relates to novel antiviral peptides comprised a membranetransiting motif wherein one or more of the amino acid residues of themembrane transiting motif are deleted or substituted for other aminoacid residues. Such substituted or fragment membrane transiting motifsmust retain antiviral activity. The antiviral peptides according to thepresent invention comprising a substituted membrane transiting motif orfragment thereof can be tested for antiviral activity via themethodology described in the following Examples. Example 2 demonstratesthat antiviral peptides comprising substituted membrane transitingmotifs retain antiviral activity, as shown by SEQ ID NO:3, described inTable 1. This derivative differs from SEQ ID NO:1 only in that bothproline amino acid residues have been placed at the carboxy terminus ofthe peptide. Table 2 lists potential active fragments of an antiviralpeptide according to the present invention.

TABLE 2 Potential Active Fragments of Antiviral Peptides SequencePurpose Peptide P11 (SEQ ID NO: 18) RRKKAAVALLP activity of n-terminal P12 (SEQ ID NO: 19) RRKKAVAVAVPAVLLALLAP half spacing of LLA motifPeptides testing role of LLA motif P13 (SEQ ID NO: 20) RRKKPAVLLAOne LLA P14 (SEQ ID NO: 21) RRKKPAVLLALLA Two LLAs P15 (SEQ ID NO: 22)RRKKPAVLLALLALLA Three LLAs Peptides for testing sequential removalof aa triplets P16 (SEQ ID NO: 23) RRKKALLPAVLLALLAP  −3N-terminusP17 (SEQ ID NO: 24) RRKKPAVLLALLAP  −6N-terminus P18 (SEQ ID NO: 25)RRKKLLALLAP  −9N-teminus P19 (SEQ ID NO: 26) RRKKLLAP −12N-terminusP20 (SEQ ID NO: 27) RRKKAAVALLPAVLLAL  −3C-terminus P21 (SEQ ID NO: 28)RRKKAAVAVVPAVL  −6C-terminus P22 (SEQ ID NO: 29) RRKKAAVAVVP −9C-terminus P23 (SEQ ID NO: 30) RRKKAAVA −12C-terminusSuch derivatives and fragments are within the scope of the presentinvention.

The peptides of the present invention can be prepared by processes whichincorporate methods commonly used in peptide synthesis such as classicalsolution coupling of amino acid residues and/or peptide fragments, and,if desired, solid phase techniques. Such methods are described in thefollowing Examples. Any method for peptide synthesis well known in theart may be used, for example, Schroeder and Lubke, in “The Peptides”,Vol. 1, Academic Press, New York, N.Y., pp. 2-128 (1965); “The Peptides:Analysis, Synthesis, Biology”, (E. Gross et al., Eds.), Academic Press,New York, N.Y., Vol. 1-8, (1979-1987); Stewart and Young, in “SolidPhase Peptide Synthesis”, 2nd Ed., Pierce Chem. Co., Rockford, Ill.(1984); Wild et al. Proc. Natl. Acad. Sci. USA, 89: 10537 (1992); andRimsky et al., J. Virol, 72: 986 (1998).

As demonstrated in the following Examples, the antiviral peptides of thepresent invention show antiviral activity against a wide range ofenveloped and nonenveloped viruses. Examples of such enveloped virusesinclude, but are not limited to, human immunodeficiency virus (HIV),vesiculovirus (VSV), herpes simplex viruses (HSV-1 and HSV-2), and otherherpes viruses, for example, varicella-zoster virus (VZV), EBV, equineherpes virus (EHV), and human cytomegalovirus (HCMV). Examples ofnonenveloped viruses include, but are not limited to, human papillomavirus (HPV) and adenoviruses.

A method for demonstrating the inhibitory effect of the antiviralpeptides of the present invention on viral replication is the well-knowncell culture technique as taught in the following Examples. Such methodsare well known in the art. See Wild et al., Proc. Natl. Acad. Sci. USA,89: 10537 (1992).

The therapeutic efficacy of the antiviral peptides as antiviral agentscan be demonstrated in laboratory animals, for example, by using amurine model as shown in Example 10.

Additionally, the therapeutic effect of the pharmacologically activepeptides of the present invention can be shown in humans via techniqueswell-known in the art. See, for example, Kilby et al., Nature Medicine4: 1302 (1998).

An antiviral peptide of the present invention would be employed as anantiviral agent by administering the peptide topically to a warm-bloodedanimal, e.g., humans, horses, other mammals, etc. The peptide may beadministered in an vehicle comprising one or more pharmaceuticallyacceptable carriers, the proportion of which is determined by thesolubility in chemical nature of the peptide, chosen route ofadministration and standard biological administration. Suitable vehiclesor carriers for the formulations of the peptide are described in thestandard pharmaceutical texts. See “Remington's PharmaceuticalSciences”, 18^(th) Ed., Mack Publishing Company, Easton, Pa. (1990).

For topical administration, the antiviral peptide can be formulated in apharmaceutically accepted vehicle containing an effective amount of theantiviral peptide, typically 0.1 to 10%, preferably 5%, of the antiviralpeptide. Such formulations can be in the form of a solution, cream orlotion. The antiviral peptides of the present invention may also be usedfor treating viral infections of the skin or part of the oral or genitalcavity. The antiviral peptides can be used individually or incombination, to treat a wider variety of viruses. Such topicalapplications could be applied to barrier materials to protect thewearer, such as gloves, condoms and other barriers known in the art.

For systemic administration, the antiviral peptides of the presentinvention may be administered by either intravenous, subcutaneous, orintramuscular injection, alone or in compositions with pharmaceuticallyaccepted vehicles or carriers. For administration by injection, it ispreferred to use the antiviral peptide in a solution in a sterileaqueous vehicle which may also contain other solutes such as buffers orpreservatives as well as sufficient quantities of pharmaceuticallyacceptable salts or of glucose to make the solution isotonic. Theantiviral peptides of the present invention can be obtained in the formof therapeutically acceptable salts that are well-known in the art.

The dosage of the antiviral peptides of the present invention will varywith the form of administration and depend upon the particular antiviralpeptide(s) chosen for the combination. Furthermore, it will vary withthe particular host under treatment. In general, the antiviral peptidesare most desirably administered at a concentration level that willgenerally afford antiviral effective results against the selectedvirus(es) without causing any harmful or deleterious side effects.

The present invention is further described with reference to thefollowing illustrated Examples. Unless defined otherwise, all technicaland scientific terms used herein have the same meaning as commonlyillustrated by one of ordinary skill in the art of the invention.Although any methods and materials similar or equivalent to thosedescribed herein can be used in the practice of the invention, thepreferred methods and materials have been described. Unless mentionedotherwise, the techniques employed or contemplated herein are standardmethodologies well-known to one of ordinary skill in the art. Thematerials, methods and Examples are illustrative only and not limiting.All references cited herein are incorporated by reference.

Example 1 Protocols and Materials

Cell Culture and Virus:

The procedures for growing Vero cells and preparing high titer stocks ofHSV-1 KOS as described in (Grau et al., Invest. Ophthal. and Vis. Sci.30: 2474 (1989)) were utilized. Vero cells were maintained incarbonate-buffered DMEM supplemented with 5% calf serum and 5% fetalbovine serum (regular medium). For some studies, cells were switched toserum-free DMEM buffered with 25 mM Hepes (pH 7.4) and allowed to adaptto that medium for 30 min prior to experimental treatments. Vero cellswere seeded into wells (0.28 cm²) of microtiter plates either at 3.5×10⁴cells/well for use 1 day later (8×10⁴ cells/well) or at 1×10⁴ cells/wellfor use 3 days later (2×10⁵ cells/well).

Plaque Reduction Assay:

Confluent Vero cell cultures in microtiter plates were infected for 1hour at 37° C. in 40 μl of medium. Except where indicated, peptidetreatments in 40 μl of medium lasted from 1 hour before through 1 hourafter infection. At the end of the adsorption period, the cultures werere-fed with 100 μl of regular medium. Plaque formation was scored 2 dayslater and the number of plaques scored per well was normalized to thenumber counted in the absence of peptide. Using an ocular micrometer,plaque size (π/2×L×S) was determined by measuring the largest plaquediameter (L) and the diameter at a 90° angle to that (S). The size ofeach of the first 40 scored plaques was measured except when a plaqueincluded less than 10 rounded cells or touched the side of the well.

Yield Reduction Assay:

Three days post-infection, Vero cell cultures in microtiter plates werefrozen (−80° C.) and thawed (37° C.) three times. Cells were suspendedby repeated pipetting and microtiter plates were spun for 10 min at700×g in a Beckman model TJ-6 tabletop centrifuge. The virus-containingsupernates were serially diluted in regular medium and titered on Verocells. Plaques were counted after staining the monolayers with crystalviolet as taught by Grau et al., Invest. Ophthalmol. Vis. Sci. 30:2474(1989).

Attachment Assay:

HSV-1 KOS was labeled with [³²P]-orthophosphate to a specific activityof 0.01 cpm/pfu. Briefly, Vero cells were infected at a moi of 5.0 andat 6 hours post-infection, [³²P]-orthophosphate (0.5 mCi/ml) was added.At 18 hours post-infection, the cells and culture medium were harvestedseparately. The cells were subjected to 3 freeze-thaw cycles and celldebris was pelleted by centrifugation at 2000×g for 10 min. Thefreeze-thaw supernatant was combined with the media and virus waspelleted by centrifugation through a 26% sucrose gradient cushion astaught by Visalli et al., Virus Res. 29:167 (1993). The viral pellet wasresuspended in PBS for use. Confluent Vero cell cultures in microtiterplates were switched to serum-free DMEM, chilled on ice, and maintainedat 4° C. After 30 min, peptides were added and 60 min later, cells wereincubated for 2 hours with ³²P-virus (2×10⁴ cpm/well). After labeling,cells were rinsed with ice-cold medium. Bound ³²P was thenquantitatively extracted with 1% SDS and 1% Triton X100 in PBS andcounted in a Beckman LS5801 liquid scintillation counter.

LacZ⁺ Virus (hrR3) Entry Assay:

Confluent Vero cell cultures in 96-well microtiter plates were switchedto Hepes-buffered serum-free DMEM, cooled on ice to 4° C. for 30 min,and infected with hrR3 for 1 hour at 4° C. in 40 μl of medium.Unattached virus was removed by rinsing with ice-cold medium. Treatmentswith antiviral peptide SEQ ID NO:1, referred to as EB, or a controlpeptide which comprised the RRKK tetra-peptide (SEQ ID NO:16) attachedto a scrambled version of the membrane transiting peptideR-R-K-K-L-A-A-L-P-L-V-L-A-A-P-L-A-V-L-A (SEQ ID NO:17) (referred to asEBX), or mock-treatments with peptide-free medium were carried out inserum-free DMEM as indicated. Virus entry was initiated by transferringcultures to 37° C. To inactivate any remaining extracellular virus,cultures were rinsed with PBS and exposed to low pH citrate buffer (40mM citric acid, 10 mM KCl, 135 mM NaCl, pH 3.0, according to Highlanderet al., J. Virol. 61:3356 (1987), for 1 min at 23° C. The citrate wasrinsed off with PBS and cultures were maintained in serum-supplementedDMEM until they were fixed with 0.5% gluteraldehyde in 5×PBS for 30 minat 23° C., stained for β-galactosidase activity for 1 hour or overnightat 23° C. with X-gal (Fisher Biotech; BP1615-1) in 1×PBS containing 2 μMMgCl₂, 1.3 mM K₄Fe(CN)₆, and 1.3 mM K₃Fe(CN)₆, and scored for thepresence of blue lacZ⁺ cells.

Virucidal Assay:

HrR3 (1.2×10⁶ pfu/ml) was incubated with various concentrations of EB orEBX for 1 hour at 37° C. in 70 μl serum-free DMEM (pH 7.4). The treatedvirus was diluted 200-fold with serum-supplemented DMEM and assayed forinfectivity approximately 1 hour later in microtiter wells seeded withVero cells (3.5×10⁴ cells/well) 1 d earlier. Forty or 100 microlitervolumes of diluted virus were adsorbed for 1 or 2 h at 37° C. and lacZ⁺cells were scored 8 hours later. In some experiments, aliquots ofdiluted virus were first dialyzed (Spectra/Por; MWCO 12-14,000)overnight at 4° C. against a 60-fold excess volume of Hepes-bufferedserum-supplemented DMEM or forced by syringe through 0.22 μm membranes(Millex-GV; Millipore) before the remaining infectious virus wasassayed.

Trypan-Blue Exclusion Assay:

Uninfected Vero cells in serum-free or serum-supplemented DMEM wheretreated for 1 hour at 37° C. with antiviral peptide SEQ ID NO:1 orcontrol peptide EBX (SEQ ID NO:17), rinsed with PBS, stained for 5 minat 23° C. with 0.4% trypan-blue in PBS, rinsed again with PBS and airdried.

Electron Microscopy:

Purified HSV-1 KOS virions (2.5×10⁷ pfu/ml) according to Visalli et al.,Virus Res. 29:167 (1993) were treated with 25 μM antiviral peptide SEQID NO:1 or the control peptide EBX (SEQ ID NO:17) in 40 μl serum-freeDMEM buffered with 25 mM Hepes (pH 7.4) for 5 to 60 min at 4 or 23° C.Aliquots (10 μl) were adsorbed to pioloform poly-L-lysine-coated gridsfor 5 min at 23° C. Grids were rinsed with PBS, stained with 2%phosphotungstic acid (PTA) in water adjusted to pH ˜6, and air dried.Alternatively, virus was pre-adsorbed to grids and treated with peptidesthereafter. A total of 4×10⁹ pfu/ml of purified HSV-1 KOS in 5 μl PBSwas applied to the coated grids for 5 min at 23° C., and the grids wererinsed once with serum-free DMEM buffered with 25 mM Hepes (pH 7.4) andtreated with 15 μl of 5 mM EB or EBX in the same medium for 30 min at37° C. The pH of highly concentrated solutions of antiviral peptide SEQID NO:1 and EBX was re-adjusted to 7.4 with NaOH prior to use. Toprevent evaporation of the peptide-containing solutions, each grid washeld in a Hiraoka flexible staining plate and covered with miniaturebell jar made from an 0.5 ml polypropylene micro-centrifuge tubes, smallenough for the 15 μl to fill half of the bell jar facing the coatedsurface of the grid. The entire assembly was then incubated in a moistchamber for 30 min at 37° C. After treatment, grids were rinsed twicewith DMEM and once with PBS before they were stained with PTA and dried.Grids were examined in a JEOL JEM-1200EX electron microscope atmagnifications of 15,000 and 40,000×.

Peptide Synthesis:

Synthesis and analysis of peptides was done at the Biotechnology Centerof the University of Wisconsin-Madison. Synthesis was carried out at a25 pmole scale using an automated synthesizer (Applied Biosystems Model432A “Synergy”) following the principles initially described byMerrifield, J. Am. Chem. Soc. 85:7129 (1963) with modifications byMeienhofer et al., Int. J. Peptide Protein Res. 13:35 (1979) and Fieldset al., Peptide Res. 4:95 (1991). The cleaved peptides were precipitatedwith cold t-butylmethylether, dissolved in water, and examined byanalytical HPLC (purity) and electrospray ionization mass spectroscopy(molecular mass, see Table 1). Peptide concentrations in solution weredetermined from absorbance readings at 215 and 225 nm as taught bySegel, Biochemical Calculations, 2^(nd) ed. John Wiley & Sons, Inc., NewYork, N.Y. (1976).

Example 2 Antiviral Activity of Antiviral Peptides

The antiviral peptide EB (SEQ ID NO:1), was an effective antiviral agentwhen present during infection of Vero cell cultures with HSV-1 KOS,blocking plaque formation as shown in FIG. 1A (●), FIG. 1B (●) and FIG.1D (◯); and reducing virus yields by up to eight orders of magnitudedepending on concentration (see FIG. 1E). Compared to a control peptideFIG. 1A (◯) and FIG. 1B (◯) EBX, the antiviral peptide EB was a far moreeffective antiviral, blocking infections at 10 or 100-fold lowerconcentrations depending on the presence (FIG. 1A) or absence (FIG. 1B)of serum.

The cytotoxic effects of antiviral peptide EB, as measured bytrypan-blue exclusion in the absence of serum, were seen only atconcentrations 100-fold higher (FIG. 1C, (●); IC₅₀=68 μM) than antiviralconcentrations (FIG. 1B, (●); IC₅₀=0.7 μM). In the presence of serum,cytotoxic effects were seen first at 200 μM EB (FIG. 1C, (Δ)). Nocytotoxic effects were associated with the control peptide EBX (SEQ IDNO:17) (FIG. 1C, (◯)).

The charged amino-terminal R-R-K-K tetramer was found to be useful forenhancing the solubility of the otherwise hydrophobic antiviral peptideEB, but does not have any important antiviral activity by itself. In thepresence of serum, no antiviral activity was associated with the freeR-R-K-K tetramer (SEQ ID NO:16) at concentrations as high as 200 μM(FIG. 1A, (▴)).

In separate experiments, it was discovered that free R-R-K-K tetramer(SEQ ID NO:16) inhibited hrR3 infection of Vero cells under serum-freeconditions at an IC₅₀ value of 1.3 mM (data not shown). We also foundthat high (up to 100-fold molar excess), but non-antiviralconcentrations of the free R-R-K-K peptide (SEQ ID NO:16) did notcompete with antiviral peptide EB activity and could not relieveinhibition of hrR3 infections due to the antiviral peptide EB (data notshown).

To inquire whether derivatives of a membrane transiting protein sequenceexhibited antiviral activity, we tested a modified antiviral peptide(SEQ ID NO:3) referred to as EBPP, in which the central proline residuewas moved to the carboxy-terminal end. This EBPP-peptide (Table 1) wastwice as active as the original EB peptide in both, plaque (FIG. 1D) andyield reduction assays (data not shown).

The EB peptide was modified to carry biotin (SEQ ID NO:2), and testedfor activity as described above. As shown in FIG. 2, the biotinylated EBwas essentially as effective as EB. Thus biotinylation of the peptidehad a negligible effect on activity.

The antiviral activity of a number of other antiviral peptides andcontrols according to the present invention were determined as describedabove. The results are shown below in Table 3. As shown in FIG. 1E,antiviral peptide SEQ ID NO:4, referred to as “LALA”, demonstratessimilar antiviral activity as EB.

TABLE 3 Antiviral Activity of Antiviral Peptides Entry VirucidalAnti-Free Blocking Activity¹ Virus Cyto- Peptide Activity¹ 37° C. 4° C.Activity¹ toxicity¹ EB 15-26  44  89 (SEQ ID NO: 1) bEB 15  35 110 21100 (SEQ ID NO: 2) EBX None None None (SEQ ID NO: 17) bKLA 11  15  454.5 15 (SEQ ID NO: 5) bKLAd_(11,12) 23  61 300 (SEQ ID NO: 6) bHOM-9 9-12 115 None 6 50 (SEQ ID NO: 7) bHOMd  7 115 None (SEQ ID NO: 8]bHOMFF 40 None None 34 >>100 (SEQ ID NO: 9) bTAT-9 26 None None 8 ~200(SEQ ID NO: 10) bTAT-9x 67 None None (SEQ ID NO: 12) ¹IC₅₀ values forall peptides

Example 3 Comparison of Antiviral Activity of Antiviral Peptide vs.Acyclovir

Vero cell cultures as prepared in Example 1 were infected with HSV-1 andassayed for virus production as described in Example 1. The antiviralactivity of an antiviral peptide according to the present invention EB(SEQ ID NO:1) was compared to the antiviral activity of the current HSVantiviral nucleoside standard, acyclovir. The two peptides were added tothe Vero cells one hour prior to infection with HSV. As FIG. 3illustrates, although acyclovir shows the highest antiviral activity atlow dosages, at high concentrations, i.e., those exceeding 10 μM of theactive ingredient, EB showed the greatest antiviral activity.

Example 4 Early Effects and Effects on Cell-Cell Spreading

It was determined that antiviral peptides according to the presentinvention act early in the viral life cycle. As shown in FIG. 4A, EB wassubstantially more effective, when present during infection and 1 hourpre- and post-infection, than when present continuously starting 1 hourpost-infection (IC₅₀=5.5 μM, (◯) vs. IC₅₀=24, (●)), respectively).Furthermore, when present before and during adsorption, EB had no effecton plaque size. When the EB peptide was present continuously afterinfection, plaque expansion was inhibited in a dose-dependent manner(FIG. 4A, (Δ); IC₅₀=12 μM). To ensure that individual plaques weremeasured reliably, cell cultures were infected at very low multiplicity(moi<0.01) and plaque sizes were measured microscopically very early (1day post-infection). As shown in FIG. 4B, in untreated control wells,plaque size was broadly distributed (black bars; mean: 66,000±6200 μm²),whereas addition of increasing concentrations of EB 1 hourpost-infection progressively shifted the distribution towards smallersize classes (e.g., 25 μM EB significantly reduced the mean plaque sizeby 70% to 6900±2600 μm²; t=6.88; shaded bars). In contrast, the presenceof EB up to 1 hour post-infection had no effect on plaque size, eventhough the number of plaques were severely reduced compared topost-infection treatment. Thus, the combined mean plaque size aftertransient treatments with 6 and 12 μM EB (68,000±11,000 μm²), wasindistinguishable from the controls. EB appeared to act at an earlystage of viral infection and reduced plaque size when added afterinfection.

Example 5 Aggregation of Virus by Antiviral Peptide

Antiviral peptides of the present invention were shown to aggregatevirus by electron microscopy. Purified virus particles at highconcentrations, as required for efficient visualization, were incubatedwith 25 μM EB, adsorbed to coated grids and stained with PTA. Theresults showed nearly all of the particles were seen in relatively fewlarge aggregates. In contrast, untreated virus, or virus particlestreated with 25 μM EBX were nearly all found individually and uniformlyscattered over the grid surface. The individual PTA-stained virusparticles within aggregates were virtually indistinguishable fromcontrol particles, indicating that EB did not induce gross structuralabnormalities in the virus particles. The EB-induced aggregates wereformed rapidly (<5 min) at room temperature as well as at 4° C.

Example 6 Antiviral Activity of Antiviral Peptide with Respect to VirusInput

Cultures were infected with hrR3 at inputs of 19, 210, and 5700 pfu/wellin the presence of various concentrations of EB and scored 8 hours laterfor lacZ⁺ cells, the IC₅₀ values obtained were 0.66, 1.2, and 11 μM,respectively, as shown in FIG. 5.

Significantly, above the intermediate input of 210 pfu/well, there was agreater increase in the IC₅₀ with increasing virus titer than below thatinput, as shown in the inset in FIG. 5. The inverse relationship betweenIC₅₀ and virus titer would be expected if EB merely acted as anaggregation agent, which should operate more efficiently, i.e., withlower IC₅₀, at the higher virus input. Thus, viral aggregation does notmake any major contribution to the antiviral activity of EB in theseexperiments. Furthermore, the fact that the antiviral activity of EBstrongly depended on virus concentrations, suggests that that theantiviral peptides of the present invention interact with viralcomponents.

Example 7 Inhibition of Viral Entry

Additional studies with pre-adsorbed hrR3 virus demonstrated that theantiviral effect or effects of an antiviral peptide of the presentinvention are related neither to virus adsorption nor to virusaggregation, but rather to inhibition of virus entry. In these studies,the hrR3 virus was pre-adsorbed to cells for 1 hour at 4° C. before icecold 25 μM EB or EBX were added in serum-free DMEM. After an additional1 hour at 4° C., cultures were shifted to 37° C. to initiate virusentry. At 15 min intervals following the temperature shift, any virusremaining outside the cells was inactivated by washing the cultures withlow pH citrate buffer. Cultures were then rinsed and returned topeptide-free serum-supplemented DMEM until they were fixed and stainedfor β-galactosidase 8 hours after the temperature shift.

As shown in FIG. 6A, virus entry in mock-treated control cultures (◯)was initiated 15-30 min after transfer to 37° C. and completed by about60 min at a level of about 340 lacZ⁺ cells per 6.5 mm² (or 1450 lacZ⁺cells/well). In cultures treated with the EB peptide, the number oflacZ⁺ cells was reduced by >90% (●). The EBX peptide did notsignificantly reduce the number of lacZ⁺ cells (▴). Essentially the sameresults were obtained when EB and EBX were added prior to virusadsorption (data not shown). When peptide was added immediately aftereach citrate treatment, EB no longer had any effect on the developmentof lacZ⁺ cells (FIG. 6B, (●); cf. FIG. 6A, (◯)). EBX also did notsignificantly inhibit the development of lacZ⁺ cells when addedimmediately after the citrate treatments (FIG. 6B, (▴)). Thus, EB had noeffect on the expression of the lacZ gene from the early ICP6 promoter,but selectively blocked viral entry.

This conclusion is strengthened by the finding that the EB-sensitivephase of infection with pre-adsorbed virus clearly precedes expressionof lacZ genes in hrR3 infected cells (FIG. 7A). Again, hrR3 waspre-adsorbed to cells for 1 hour at 4° C., unattached virus was rinsedoff, and cells were kept for an additional hour at 4° C. Cultures werethen transferred to 23° C. for 30 mm before they were switched to 37° C.The more gradual change to 37° C. allowed cell layers to remain intactthrough subsequent frequent medium changes. Immediately following viraladsorption, cells were treated with 50 μM EB for 1 hour periods atconsecutive 1 hour intervals. Between 1 and 4 hours post-infection,virus entry was inhibited by 70-80%. Thereafter, infection was no longersignificantly inhibited (FIG. 7A, (●)). Parallel cultures wereimmediately fixed after mock-treatments and stained with X-gal. In thesecultures, blue (lacZ⁺) cells first appeared 7 hours post-infection andtheir number increased nearly linearly for the next 3 hours (FIG. 7A,(◯)). By 7 hours post-infection, EB ceased to be inhibitory. Thus, EBonly blocked virus entry during an early brief sensitive period and hadno effect on the expression of the lacZ gene and the development ofβ-galactosidase activity once the virus had entered the cell. As shownin FIG. 7B, EB inhibited entry of pre-adsorbed virus in a dose-dependentmanner with an IC₅₀=15 μM (●), whereas EBX was less effective (IC₅₀˜100μM; (◯)).

Example 8 Virucidal Effects of Antiviral Peptide

It was found that the binding of antiviral peptides of the presentinvention to virus particles leads to irreversible virus inactivation.Virucidal assays were performed with hrR3. In the first experiment (FIG.8A), EB inhibited the infectivity of virions in aconcentration-dependent manner with an IC₅₀=44 μM (●), whereas EBX hadno inhibitory effect (◯). In the second experiment, in which slightlyhigher concentrations of EB were required to achieve inhibition (FIG.8B, (●); IC₅₀=69 μM), we also found that the treated virions wereirreversibly inactivated. That is, aliquots of EB-treated and thendiluted virions could not be re-activated during overnight dialysisagainst serum-containing medium that could have trapped anyreversibly-bound EB (cf. FIG. 1, (●); A vs. B). Instead, virionsrecovered after dialysis (31% at any EB concentration) remainedinactivated exactly like the non-dialyzed controls (FIG. 8B, (Δ) vs.(●)).

To assess possible contributions of viral aggregation to viralinactivation, additional aliquots of EB-treated and subsequently dilutedvirions were filtered through 0.22 μm membranes before they were assayedfor remaining infectivity. In the absence of, or at low concentrationsof EB (≦3 μM), 80-85% of the virions were trapped on the membranes. Theremaining virions, however, were retained only once exposed to higher EBconcentrations, which enhanced membrane adhesion and/or caused viralaggregation (FIG. 8B, (▴)). Such changes in the adhesive properties ofvirions were induced well below EB concentrations required for virusinactivation (FIG. 8B, (▴) vs. (●), (Δ)).

The effects of the most severe EB treatments were examined by electronmicroscopy of PTA-stained virions that had been pre-adsorbed to grids(to avoid aggregation) and exposed to 5 mM of peptide. The EB-treatedvirions looked essentially the same as mock-treated virions, except thatcontours of the viral envelops in the EB-treated particles were lesspleomorphic, suggesting EB stabilized virions. At 5 mM, EBX had the sameeffect as EB.

Example 9 In Vivo Activity of Antiviral Peptide

The antiviral peptides according to the present invention demonstrate invivo activity when topically applied. HSV-1 strain KOS was incubated for1 hour with either the EB peptide or the EBX peptide at a concentrationof 25 μM at room temperature in PBS. Groups of ten mice each were theninfected via corneal scarification with 5.0×10⁵ plaque forming units aswe have described previously (Brandt et. al., J. Virol. Meth. 36, 209(1992).

Briefly, the mice were anesthetized with halothane, the cornea wasscratched 3 times horizontally and 3 times vertically, and a 5 μl dropcontaining virus was placed on the cornea. The mice were then returnedto their cages and allowed to recover. A control group infected with KOSbut not exposed to peptide was also included. The mice were not treatedwith peptide after infection.

At various times post-infection, the severity of ocular disease wasmeasured as we described previously (same ref.) Briefly, vascularizationwas scored: 0, no vascularization; 1+<25% of the cornea involved;2+25-50% involvement; and 3+>50% involvement (see FIG. 9A). Keratitiswas scored: 0 no corneal clouding; 1+cloudiness, some iris detailvisible; 2+cloudy, iris detail obscured; 3±cornea totally opaque;4+cornea perforated and cloudy (see FIG. 9B). Data are reported as themean disease score on each day for each of the three groups. The resultsare illustrated in FIG. 9.

The following references are additionally incorporated by reference:

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What is claimed is:
 1. A peptide according to formula 2 (SEQ ID NO: 15)(X1)_(n)-P-A-V-L-L-A-L-L-A-(X2)_(m)  formula 2 wherein X1 and X2 areselected from one or more charged amino acid residues selected from thegroup consisting of arginine, lysine and combinations thereof, furtherwherein n has a value of 0 or 3-10 and m has a value of 0 or 3-10 andwherein either m=0 or n=0.
 2. The peptide of claim 1, wherein X1 and X2are selected from one or more positively charged amino acid residuessuch that each X1 and each X2 may be the same or different positivelycharged amino acid residues.
 3. The peptide of claim 1, wherein thepeptide has a sequence according to SEQ ID NO:
 21. 4. A compositioncomprising the peptide of claim 1 and a pharmaceutically acceptablecarrier.
 5. The composition of claim 4, wherein the composition iseffective for treating herpes simplex virus type 1 ocular disease.
 6. Acomposition comprising the peptide of claim 3 and a pharmaceuticallyacceptable carrier.
 7. A method of treating a herpes simplex virustype-1 ocular infection in a warm blooded animal comprisingadministering to the animal an effective amount of the compositionaccording to claim 4.